R8 Front Slim Radiator - push or suck?
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  1. #1
    Fellow Frogger! R8 Dream's Avatar
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    Default R8 Front Slim Radiator - push or suck?

    As some of you know by now, I did the rear to front radiator conversion to my R8, similar to the way the Alpine A110's have it.

    It might sound like a stupid question, but which way should the fans be blowing into the slimline radiator?

    should the fans be "sucking" or "pushing"?

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    logic says should be pushing against the radiator?

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    COL
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    It looks like you have the fans mounted behind the radiator so the fans should be sucking the air through the radiator.

    This is the most efficient setup.
    Regards Col

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    Thanks Col, my logic was obviously 180deg around.

    will give it ago now.

    thanks

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    You know, after 22 years with a Peugeot 306, in parallel Citroens Xantia, BX and CX, all with pusher fans, I don't think it matters at a practical level. They never overheat if the fans are working when required. I think I'd rather suck and leave the full face of the radiator exposed, i.e. high pressure across all of it, but the ducted fans do protect the radiator. What really does matter, I reckon, is a good air exit pathway from the low pressure side of the radiator out under the car. 4cvg's car has nice ducting, to give one example.
    JohnW

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    "Sucking" fans don't need a fan shroud.

    All of the air they draw is through the radiator.

    Unlike "blowing" fans.

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    In racing applications where the cooling system is at the absolute limit of performance and needs to remove a lot of heat energy the general proven practice is no fan because a fan in front of the radiator restricts inlet air volume and speed.

    Sometimes on an extended pit stop you may see a team member run out to hold a portable fan in front of the car to bring the radiator temps down until it moves off and gets the air flowing again.
    For high performance cars used on the street, occasional track days plus some limited competition, best practice is to put the fan behind the radiator sucking.

    Most road cars dont go as fast as race cars and they dont have the severe demands on the cooling system therefore a front fan pushing is OK when you are driving in city traffic.

    It all depends on how fast you want to go and how much horsepower you have.
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    1000+ Posts renault8&10's Avatar
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    If it pushes, it would also be fighting against the natural flow Renault designed for that vehicle (albeit when the radiator was down the back, but still).
    KB


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    Quote Originally Posted by Bustamif View Post
    In racing applications where the cooling system is at the absolute limit of performance and needs to remove a lot of heat energy the general proven practice is no fan because a fan in front of the radiator restricts inlet air volume and speed.

    Sometimes on an extended pit stop you may see a team member run out to hold a portable fan in front of the car to bring the radiator temps down until it moves off and gets the air flowing again.
    For high performance cars used on the street, occasional track days plus some limited competition, best practice is to put the fan behind the radiator sucking.

    Most road cars don’t go as fast as race cars and they don’t have the severe demands on the cooling system therefore a front fan pushing is OK when you are driving in city traffic.

    It all depends on how fast you want to go and how much horsepower you have.
    Don't disagree, but our cars have had their times cruising at 40 degrees at 100+ kph, with perfectly adequate cooling, so not exactly city traffic. Trouble is, and sort of the same subject, because they DO have fans, if they fail, or one fails, you don't necessarily get adequate cooling, especially in city traffic on a 40 degree day.

    It might go down to where the fan can be fitted!! I wonder whether PSA put the fans in a pusher location for space reasons. When we were hit by two falling tree branches driving near home (the probability of that accident being????) the fan shroud actually saved the radiator from damage!
    JohnW

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    I have had this discussion before after spending the best part of a year and a lot of money trying to get the 1600 R8G to run under 95 degrees on a 40 degree day with a radiator in the back. I even got old mate Paul Wheel to make a special, really big alloy rad based on the V8SC unit with huge fans and all the best gadgets to exceed the CFM of a normal engine driven fan. Eventually I had to concede that a front rad was the only way to go and put an A110 style front rad with the fan behind sucking. Now 75 degree engine temp at constant 115 kph on a 40 degree day or sitting in Sydney traffic.

    I admit that my Alconi will run at constant 75 to 80 degrees on the same 40 degree day with a standard rear radiator. Single side draft 45DCOE weber, big cam, headers 1400cc just does not create the same thermal load that a 1600 R12G/A110 spec (plus a bit) motor does.

    That R8G Frans runs in NZ really needs the front radiator because of the HP he is making. Same for others racing seriously and competing in circuit racing with an R8G making good horsepower and driven hard. Steve Swans car also comes to mind.

    Some very experienced wise heads here all told me so but I had to find out for myself.

    If you are going to run a front radiator and are thinking of competing on a race track, you may as well get it right to begin with and put the fan behind.

    The other big plus of the front radiator with an electric fan sucking is that if the fan stops it only causes a problem in traffic. As long as you are moving over about 40-50 kph the cooling system is still working fine, provided you keep the leaves and branches out of the radiator inlet.
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    Out of interest, and I hope not hijacking the thread, did you ever try a waterless coolant with a high boiling point? It might be they aren't allowed on the track I suppose. It was one of the avenues I started exploring until I found a radiator with three rows of tubes solved my particular problem. Really interesting - I wasn't considering really high heat generation.
    JohnW

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    Default R8 Cooling

    I have since discovered that only one fan was working, but a blow relay ( there are 2 - one per fan) was the cause. Fitted a new relay and both working again. I am using the Davis Craig digital therm attic controller ( part no. #0444).

    Anyway filled up the filler as much as I could and ended up putting about 8 litres.

    i have fitted a bleed valve just above the radiator, which is just below the height of the filler cap at the rear of the car ( again similar set up to the A110).

    started the engine and ran it to about 90 deg, but noticed the fans had not kicked in. I turned on the manual over ride and the front fans kicked it. But I noticed that the tubes leading into the front radiator and the radiator itself was still cold.

    The water pipes leading in and out of the water pump (at the rear) were very hot.

    next the expansion bottle started bubbling and steaming. It was beginning to fill up with very hot water?

    i am at a loss as to why the water may not be making its way to the front and around the system?

    i am sure there is air in system, is this what is causing the problem?

    Do I bleed ( get the air out) when the engine is full warmed up? Tried this but nothing?

    can someone give me some guidance as to what I may be doing wrong or missing an important step?

    i would appreciate if some one could give me a step-by-step process as to how to properly bleed the air out of the system and get it working properly. As I have never used this type of cooling system, but had plenty of experience with "conventional" ford/Holden systems, I am at a loss with this.

    so close yet so far away again!

    Angelo

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    Quote Originally Posted by renault8&10 View Post
    If it pushes, it would also be fighting against the natural flow Renault designed for that vehicle (albeit when the radiator was down the back, but still).
    KB, that makes sense ��

    Thanks

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    COL
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    My Alpine almost self bleeds, I open the bleeder at the front and just fill the system with coolant.
    When the coolant starts to run out of the front bleeder I close it and continue to fill the rest of the system.
    I also open the bleeder at the heater and do the same there.
    Them top up the system and start the car.
    Regards Col

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    Quote Originally Posted by COL View Post
    My Alpine almost self bleeds, I open the bleeder at the front and just fill the system with coolant.
    When the coolant starts to run out of the front bleeder I close it and continue to fill the rest of the system.
    I also open the bleeder at the heater and do the same there.
    Them top up the system and start the car.
    that is was I was told to expect ( by Rob Sealey), but it doesn't?

    do you do this cold? How then would then you do this with the thermostat closed?

    i also deleted the heater, so only bleed point is at the front. I use a similar hose and bleed tap as used in the A110 (Rob's A110)

  15. #15
    1000+ Posts Frans's Avatar
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    Angelo,

    I have done many front engine radiators and the easiest way that needs almost no bleeding is to have the expansion bottle in front. Extend the bleed you say you have to the expansion bottle and keep it in front. Open the expansion bottle and fill the radiator at the back. The water should be rising in the bottle before it runs over at the back. You can pour as much as you like but you won't fill the bottle in front because it is lower than your filler cap. When the bottle is 3/4 full, go to the front and I normally take the bottle out of it holder and lift it high. Mine can stand on the battery box. Then I walk back to the rear and sooner or later the water will drain from the front bottle and fill the neck at the back. Let the water run out at the back until it is at the MAX mark on the bottle then replace the cap at the back. the level will remain constant in front. Fit the bottle's cap and then lower it into it holder that you made or are going to make. I am a loner and I do it alone everytime and it works everytime.

    I do not have the luxury of an electric pump and I have not seen the inside of such a pump but I know that when we started Ross's Dauphine the first time the electric pump did give us problems and we had to switch it manually on to get the water filling the pump body.

    The switch to turn on the fans should be mounted at the engine. This way it will turn the fans on quicker and then the cooled water will only need to flow from the front to the back to start cooling the engine. If it is mounted in front, the hot water needs to flow all the way to the front and turn the fan on and only then the cooled water can make its way to the engine. One fan is more than enough. 2 fans is extra weight. The fan works only at slow and idling speeds and then the car releases very little energy and the 1 fan is enough to cool it. When I race there is no fan running because there is plenty of air going through the front air dam. My radiator is enclosed in a tunnel that I made from that plastic flute sheets and the air that enters the fish mouth is forced to go through the radiator. There is no escape holes on the sides.

    I think you have to try a few times and important is to feel the front hoses. because you don't have a thermostat you should feel it reasonably quick.

    Keep in mind that my radiator is lying almost horisontal. The bottom is at he front level with the number plate panel bottom and the top is at the rack and pinion side. That gives me about a 10 degree from horisontal angle but my advantage is that I can fit a decent size Nissan Primera radiator in there by utilising all the space to the rack and pinion. Because it is a sealed system the is no rule that says it has to be vertical. The G Turbo in ZA had a horisontal radiator as well running cool with 118 or 119 Kw at the wheels.So, don't despair, it will work. Sort the method out and take note of what caused the airlock. My guess is the water pump.

    Frans
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    Quote Originally Posted by R8 Dream View Post
    that is was I was told to expect ( by Rob Sealey), but it doesn't?

    do you do this cold? How then would then you do this with the thermostat closed?

    i also deleted the heater, so only bleed point is at the front. I use a similar hose and bleed tap as used in the A110 (Rob's A110)
    You should not have a thremostat with the electric pump.
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    Angelo,
    I just read a quick summary of the fan controller 0444 and that is not good in my opinion because the sensor is mounted in the airflow of the radiator and that is what I meant by waitin a long time to come on. If yours is mounted in the front airstream then cahnge it befor eyou drive the car. What happens at a traffic light or traffic jam? the car standing still with no airflow so the sensor will not turn on. No air is going over at standstill.
    AIR TEMPRETURE APPLICATION:

    It senses air temperature as it passes through the radiator and has an adjustable temperature range of 40C to 110C (104F to 230F).
    The Temperature Sensor is placed in the radiator fin section as close to the hot coolant inlet as possible, no need to cut hoses or can be placed directly into the coolant system.

    Frans.
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    Quote Originally Posted by Frans View Post
    You should not have a thremostat with the electric pump.
    Just to clarify Frans, I am not running an electric pump, just a standard R8/10 water pump.

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    Quote Originally Posted by Frans View Post
    Angelo,
    I just read a quick summary of the fan controller 0444 and that is not good in my opinion because the sensor is mounted in the airflow of the radiator and that is what I meant by waitin a long time to come on. If yours is mounted in the front airstream then cahnge it befor eyou drive the car. What happens at a traffic light or traffic jam? the car standing still with no airflow so the sensor will not turn on. No air is going over at standstill.
    AIR TEMPRETURE APPLICATION:

    It senses air temperature as it passes through the radiator and has an adjustable temperature range of 40C to 110C (104F to 230F).
    The Temperature Sensor is placed in the radiator fin section as close to the hot coolant inlet as possible, no need to cut hoses or can be placed directly into the coolant system.

    Frans.
    Frans
    I called Davis Craig last week, and he said that it was fine with my set up, but recommended at I set the thermostat to 15deg below the ideal running temp. So for 80 deg running, I set the thermostat at 65deg.
    so by I figure by the time the water runs from the engine at the back to the front radiator it still should be hot enough to kick in the fans.

    i have a manual override switch that can be kicked in at anytime.

    you are right, when travelling the air through moving will cool the water, but it's when stationary that I am concerned.

    i just recalled now watching Dave C fill my old R8 (standard rear radiator) and he used an elongated alum tube fixed into the plug of the rear radiator with a container of around 2 litres on the top. It was around 1.5m above the rear radiator and Dave filled it from up high. I figure this was to give a decent head of water to force the water through the system.

    i will give it another go tomorrow, but it's just frustrating.

    out of interest, how many litres of water do you typically use?(yes I am using water first to make sure the system holds under pressure, and when happy it works I will refill with coolant - cheaper and less mess to test with water)

    Angelo

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    Quote Originally Posted by Frans View Post
    I think you have to try a few times and important is to feel the front hoses. because you don't have a thermostat you should feel it reasonably quick.
    Frans, sorry just to be clear, I am running a thermostat (the one in the radiator hose just above the water pump). Should I take this out and run without one?

    Angelo

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    Oops, I thought when you mentioned Craig that you had the full system.

    The only thing I do to all my cars' thermostats is to drill a 2,5mm hole in it next to the plug in the fixed part of it. It will allow the air to escape as the water level rise in the engine. Then you don't need to run the engine and wait for it to open.

    Frans
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    Angelo,
    I'm a bit slow but all these things pop up in my mind some time later.

    I still don't like the idea of the sensor in the air in the front. There will be a time after the bleeding and circulation is sorted that will take time and it won't be working. It might work at idling where the sensor turns on with ambient temp around the radiator (no air flow) and then it is going to come on too soon when driving slow and there is a little air flow. In other words there will be no set temps turning the fan on and off, it will vary and lets hope it does save the engine. If the setting of the switches are a bit low the thermostat and fan will be fighting each other. At the engine side the thermostat will be trying to heat the engine and at the radiator the fan switch will try cooling the engine. That is why it is very important that in a standard application the thermo switch has to be a higher temp rating than the thermostat. If not, the fan will run continuously while the thermostat is battling is arse off to get some temp in the engine.

    I would like to see some second opinions here because I might be overlooking something.

    Frans.
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    Interesting. Our Citroen CX has both an air temperature sensor and a coolant sensor, one for low temp fans (in series electrically, so running on 6V)) and one for high temperature (in parallel electrically, so running on 12V). I don't much like the arrangement but it usually works.

    I agree with Frans I think. If it were mine, I'd like the fan switch to be measuring coolant near the engine outlet, directly, not the surrogate of air temperature, which is (a) indirect and (b) dependent upon airflow. Could it be fitted onto the head, measuring the metal temperature like the 16TS gauge sensor unit. If you buy one of those aftermarket digital units, the sensor fixes to the head too, not in the coolant. That approach seems to work, as ally is pretty fast at conducting temperature. I think these, or one like it, have a switching option so you could set the temperature for alarm or a fan relay and see the temperature indicated directly. You'd need to get the sensor location right mind you.

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    Just a thought. Good luck with it Angelo.
    Last edited by JohnW; 26th March 2017 at 12:10 PM.
    JohnW

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    On following your logic Frans, I get what you are saying and it make sense.

    Davis Craig did mention that there is a new version of this set up (V3) which as I understand it can measure both water and air temp. The version I have is V1, as I bought it and fitted it in 2014.

    I might get back on the phone tomorrow to ask these questions as see if they can adequately answer this.

    I though going 'high tech' was a good idea, but liek with any new technology, there must be proper development time too.

    I have fitted (again holden, ford) thermo fans before using the old fashion dial to set the temp, but the probe was inserted at the radiator outlet under the rubber hose and clamped up hard. always worked, although looked a bit crude.

    I have taken the rest of the weekend off to watch the F1 GP, as I am just over it again!

    I will have a think about it all and no doubt get back to it next weekend.

    Angelo

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    COL
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    My Alpine and R12 have the temp sensor for the fan in the exit side of the radiator.

    Theory here is when there is not enough air passing through the radiator to cool the coolant the fan will come on to assist, seems to work ok.
    Regards Col

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